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| author | Brian Gerst <brgerst@gmail.com> | 2016-05-04 22:44:36 -0400 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2016-05-05 08:37:30 +0200 |
| commit | 092c74e420952c7cb68141731f2b562245b51eeb (patch) | |
| tree | c4c234dfa72513512a503c7f3e4486d78a00e16f /arch/x86 | |
| parent | 1fb48f8e54e5ed4d3d8599ba7e83f1f60530c81c (diff) | |
| download | linux-0-day-092c74e420952c7cb68141731f2b562245b51eeb.tar.gz linux-0-day-092c74e420952c7cb68141731f2b562245b51eeb.tar.xz | |
x86/entry, sched/x86: Don't save/restore EFLAGS on task switch
Now that NT is filtered by the SYSENTER entry code, it is safe to skip saving and
restoring flags on task switch. Also remove a leftover reset of flags on 64-bit
fork.
Signed-off-by: Brian Gerst <brgerst@gmail.com>
Acked-by: Andy Lutomirski <luto@kernel.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Borislav Petkov <bp@suse.de>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1462416278-11974-2-git-send-email-brgerst@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch/x86')
| -rw-r--r-- | arch/x86/entry/entry_32.S | 4 | ||||
| -rw-r--r-- | arch/x86/entry/entry_64.S | 3 | ||||
| -rw-r--r-- | arch/x86/include/asm/switch_to.h | 4 |
3 files changed, 1 insertions, 10 deletions
diff --git a/arch/x86/entry/entry_32.S b/arch/x86/entry/entry_32.S index 10868aa734dc0..c84d99bfff94e 100644 --- a/arch/x86/entry/entry_32.S +++ b/arch/x86/entry/entry_32.S @@ -209,8 +209,6 @@ ENTRY(ret_from_fork) call schedule_tail GET_THREAD_INFO(%ebp) popl %eax - pushl $0x0202 # Reset kernel eflags - popfl /* When we fork, we trace the syscall return in the child, too. */ movl %esp, %eax @@ -223,8 +221,6 @@ ENTRY(ret_from_kernel_thread) call schedule_tail GET_THREAD_INFO(%ebp) popl %eax - pushl $0x0202 # Reset kernel eflags - popfl movl PT_EBP(%esp), %eax call *PT_EBX(%esp) movl $0, PT_EAX(%esp) diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S index 6344629ae1ce7..9ee0da1807edf 100644 --- a/arch/x86/entry/entry_64.S +++ b/arch/x86/entry/entry_64.S @@ -372,9 +372,6 @@ END(ptregs_\func) ENTRY(ret_from_fork) LOCK ; btr $TIF_FORK, TI_flags(%r8) - pushq $0x0002 - popfq /* reset kernel eflags */ - call schedule_tail /* rdi: 'prev' task parameter */ testb $3, CS(%rsp) /* from kernel_thread? */ diff --git a/arch/x86/include/asm/switch_to.h b/arch/x86/include/asm/switch_to.h index 751bf4b7bf114..8f321a1b03a1a 100644 --- a/arch/x86/include/asm/switch_to.h +++ b/arch/x86/include/asm/switch_to.h @@ -39,8 +39,7 @@ do { \ */ \ unsigned long ebx, ecx, edx, esi, edi; \ \ - asm volatile("pushfl\n\t" /* save flags */ \ - "pushl %%ebp\n\t" /* save EBP */ \ + asm volatile("pushl %%ebp\n\t" /* save EBP */ \ "movl %%esp,%[prev_sp]\n\t" /* save ESP */ \ "movl %[next_sp],%%esp\n\t" /* restore ESP */ \ "movl $1f,%[prev_ip]\n\t" /* save EIP */ \ @@ -49,7 +48,6 @@ do { \ "jmp __switch_to\n" /* regparm call */ \ "1:\t" \ "popl %%ebp\n\t" /* restore EBP */ \ - "popfl\n" /* restore flags */ \ \ /* output parameters */ \ : [prev_sp] "=m" (prev->thread.sp), \ |